4 A PECULIAR GROUP OF TRONATTAS. 



the indical or on the polHcal face, but it is never chipped 

 on both faces at the same time. The fundamental dif- 

 ference from the palaeoHthic implement, in which one 

 and the same edge is chipped on both faces, is obvious. 



Another characteristic feature of these implements is 

 the flat, frequently smootih, indical face. In the majority 

 of the tronattas the indical face is strongly convex ; in 

 this group it is quite flat — in fact it could be used as a 

 pollical face — and I believe this flatness accounts for the 

 marginal chipping not being strictly limited to the in- 

 dical face. I particularly wish to point out that not a 

 single specimen has come under notice w^hich, having* 

 the usual convex indical face, exhibits marginal chip- 

 ping on the pollical face. It is, therefore, evident, that 

 a flat indical face which could just as well serve as polli- 

 cal face was the essential condition for bi-faced mar- 

 ginal chipping. 



This class of implements is very rare : I doubt 

 Whether it represents even i per cent, of the total 

 number. In the large number of specimens I have 

 collected there were only about 40 in all. 



The finest specimen (PI. I., fig. i), was found at the 

 Old Beach, and is probably uique. It is a tronatta of 

 24}^ mm. length and 34 mm. breadth, weighing 480 grs. 

 It is broader in the middle than at both ends ; the upper 

 one is sharply pointed, while the lower one is less so. 

 The largest breadth is considerably below half of the 

 length, and this gives it a peculiar leaf-shaped form, 

 particularly as the two lateral edges are slightly convex.. 

 The pollical face, though smooth, is not quite flat, show- 

 ing the wrinkles peculiar to conchoidal fracture. The 

 indical face, though flat on the whole, is divided by a 

 somewhat irregular longitudinal ridge, which runs close 

 to the left side. The left edge shows the usual chipping 

 almost from point to point, but the right edge is only 

 chipped ot the lower half, and all working abruptly 

 ceases just above the middle of the length. On turning- 

 to the pollical face, we see that the chipping exactly 

 commences at that point where it ceases on the indical 

 face, and continues to the end of the right lateral edge. 

 Now, as the chipping of the indical face was produced 

 by blows directed from the pollical face towards the in- 

 dical face, and that of the pollical face by blows directed 

 in the opposite wa}', the effect is rather a curious one. 



